How much of a series should be complete?

The question is simple- if what you're writing is a part of a series, trilogy, etc.; how much of it should be complete before pursuing a publisher?
I've written what I consider to be the first book in my proposed trilogy, did some editing and am sending it out for peer review soon. Am I jumping the gun a bit to search for a publisher now? Or should I wait until the work is done and propose the trilogy as a whole?

Sent from Samsung Galaxy S4 Using Tapatalk

__________________

"If I knew then what I know now, I'd stay six years old." -"Thrones" by Alexisonfire